1. Field of the Invention
The present invention relates to apparatus for treating air in an evaporative cooler or the like and more particularly to such an apparatus which is unusually well suited to producing a volume of treated air having a selected dry and wet bulb temperature; and which further has a component configuration which permits the apparatus to utilize outside ambient air for cooling and return air for pre-cooling, or alternatively for heating; the apparatus acquiring a variety of noteworthy performance characteristics by mounting its associated components in a configuration which is compact, lightweight, and energy efficient.
2. Description of the Prior Art
The beneficial effects of employing evaporative cooling for the purpose of reducing the temperature of an ambient airstream has been known for some time. The evaporative cooling technique is usually employed, with good success, in a number of specific environments. More particularly, evaporative cooling has been used occasionally for the air cooling of machines where higher humidities can be tolerated; for the cooling of industrial areas where high humidities are required, such as in textile mills; and for comfort cooling in hot, dry climates, where the partial saturation of the ambient airstream results in the production of cool air at acceptable humidities.
It is well understood that evaporative cooling takes place when non-saturated ambient air is mixed with a source of water. During this mixture process, a portion of the ambient airstream's sensible heat transfers from the air to the evaporating water; the sensible heat which has been transferred then returns to the airstream as the latent heat of water vapor. The foregoing exchange of heat energy is thermally isolated, or adiabatic, and continues until the ambient airstream is saturated with water vapor and the air and water temperatures are equal. With a suitable apparatus, the air temperature of the ambient airstream approaches within a few degrees of the theoretical limit, i.e. the wet bulb temperature. In its most simplistic form, evaporative cooling is carried out by blowing relatively dry, warm air through a wet mat.
Although direct evaporative cooling is quite effective in providing comfort cooling in warm, dry climates, it becomes less effective as the dry bulb and therefore the wet bulb temperature increases. It has long been known that the sensible pre-cooling of the relatively dry air by means of indirect evaporative cooling before passing it into a direct evaporative cooling process extends the theoretical potential of evaporative cooling below the ambient airstreams wet bulb temperature. The employment of an apparatus which pre-cools the relatively dry airstream before the direct evaporative cooling process makes evaporative cooling much more competitive with refrigeration type air conditioning by providing substantially the same comfort level while utilizing far less power.
The prior art is replete with examples of evaporative cooling devices which employ the technique of pre-cooling the ambient airstream prior to subjecting it to direct evaporative cooling. However, such prior art devices have suffered from several chronic problems which have prevented their being widely accepted for common usage. A lack of cooling capacity; inefficiency; and unusually large physical sizes have been the primary impediments. These problems are compounded in evaporative cooling devices which have been developed for use in a residential environment inasmuch as the systems that are currently available, do not appear to balance the practical needs of the structure and the interrelated parameters of efficiency; cooling capacity; physical size; and cost in an apparatus which is capable of both heating and cooling the structure. Although evaporative cooling systems can be found which will meet or exceed any specific parameter listed above, it is highly probable that such a system may become totally unacceptable for a major segment of the market due in large measure to technical compromises which must be made to reach the desired performance characteristic. For example, an analysis of the prior art systems reveals that where a plurality of heat exchangers are deployed or assembled in sequence for the purpose of pre-cooling a stream of ambient air, they are often positioned with little regard for the additional marginal cooling effect which they may individually contribute. As a result, there is often a significant pressure drop between the additional heat exchangers, thus requiring the utilization of larger horsepower air movers to maintain the effectiveness of the evaporative cooler and to control the pressure drop.
Another chronic difficulty encountered in prior art evaporative cooling devices which have been adapted for industrial or residential use is that they nearly all lack an efficient heating system or means for conveniently shifting from the use of outside ambient air, and return air for pre-cooling, to the exclusive use of return air for heating.
Still another problem encountered in prior art evaporative cooling devices which have been designed for industrial or residential use is the propensity for these apparatuses to move large volumes of ambient air through relatively small cross-sectional areas; or to urge the ambient air through various flow area changes, or turns in the apparatus. These prior art arrangements cause severe pressure drops in the air flow.
Therefore, it has long been known that it would be desirable to have an improved apparatus for treating air which could be employed in a wide variety of different environments; which could be manufactured and purchased at moderate cost; which is both highly efficient in operation and is compact; and which simultaneously reduces to an absolute minimum the assorted problems associated with evaporative or other types of coolers.